Collected edition upset second writer (American) (7)
I believe the answer is:
omnibus
'collected edition' is the definition.
(I've seen this before)
'upset second writer american' is the wordplay.
'upset' shows that the letters should be reversed in order.
'second' becomes 'mo' (both are short periods of time).
'writer' becomes 'nib' (something which writes).
'american' becomes 'US' (United States).
'mo' backwards is 'om'.
'om'+'nib'+'us'='OMNIBUS'
(Other definitions for omnibus that I've seen before include "reading this" , "One can expect to be moved by this" , "Travelling" , "Anthology" , "that may be moving?" .)